1. Field of the Invention
The invention relates to an apparatus and a process for hardening the cutting edges of saws, especially for working wood, as well as knives, cutting tools and punching tools for working wood, paper, paperboard, plastic, leather or textiles, by an energy beam which is passed over the cutting edge of the tool to be hardened. Saws, knives or cutting tools and punching tools experience wear at the cutting edges. The useful life of these tools depends on the quality of the cutting edge, on the material cut and on the cutting output. At the end of their useful life, these tools are either reground or scrapped. Many types of saws, knives, cutting tools and punching tools are made of carbon steel, which can easily be hardened by heating and subsequent rapid cooling. But since such hardening always results in a reduction in strength, great hardness is desired only in the area of the cutting edges. The other parts of a saw, a knife or a cutting tool should have lesser hardness, but greater strength.
2. Description of the Related Art
Known methods for partially hardening cutting edges use electron or laser beams as the energy source. A disadvantage exists with the known electron beams or laser beams in that they are complicated devices. For this reason, such processes are hardly used in practice.
Another known hardening process is inductive hardening. After grinding the cutting edge, the cutting edge area is heated by an eddy current, generated by a high-frequency magnetic alternating field, and hardened by rapid cooling.
Furthermore, it is known from WO 83/00051 to carry out surface hardening of flat areas by means of a plasma beam. Hardening cutting edges by plasma beams was not considered until recently, however, because plasma beams are unstable.
In saws, welding stellite onto the tooth tips is known. The stellite material welded on is subsequently ground to the desired pointed tooth shape. However, this process is very complicated. It is an object of the present invention to provide a process for hardening the cutting edges of saws, knives, cutting tools and punching tools in which an energy beam which is simple to produce and cost-effective to operate is used.